1. Field of the Invention
This invention relates to an electrically bendable endoscope apparatus which is bendable at a fixed speed.
2. Description of the Related Art
Recently, there has been extensively used an endoscope whereby organs within a body cavity can be observed by inserting an elongate insertable part into the body cavity or, as required, various therapeutic treatments can be made by using a treating instrument inserted into a treating instrument channel.
Also, an industrial endoscope has been extensively utilized to observe and inspect flaws and corrosions within pipings, such as in a boiler, gas turbine engine and chemical plant and within the body of an automobile engine.
Such an endoscope generally has a mechanism for bending a bendable part on the tip part side and is provided with such electrically driving means as an electric motor to drive this bending mechanism. Such an electrically bendable endoscope is combined with a bending controlling apparatus for controlling the bending of this endoscope and a light source apparatus so as to form an electrically bendable endoscope apparatus.
As shown in the publications of Japanese Patent Application Laid Open No. 317423/1989, Japanese Patent Application Publication Nos. 12571/1990 and 59329/1988 and Japanese Patent Application Laid Open No. 69523/1983, the disclosed electrically bendable endoscope apparatus has, in the bending controlling apparatus, a controlling means for controlling the bending speed with the bending operation switch which controls time, operated amount and operated force amount in order to improve its operability.
However, in the conventional electrically bendable endoscope apparatus, as the bending speed varies with the bending operation switch controlling time, operated amount, Operated force amount or operated state, it will take time to be accustomed to the operation and particularly beginners will find it hard to operate the bending operation switch. Therefore, in the above-mentioned apparatus, with a slight operation, the bending will be large, will be quick or will quickly become slow, what degree of operation may be made to obtain a predetermined bent angle will not be able to be easily caught and, in order to make an operation as desired, one must be skilled in the operation.
Also, as shown in the publication of Japanese Patent Application Laid Open No. 69523/1983, a fine adjusting bending switch is provided besides the bending operation switch but the bending speed is not controlled thereby to be fixed (constant). Therefore, there is the problem that, when the bending angle is large, the torque of the motor will be weaker than the tension of the wire for bending, therefore the bending speed will be low and the fine adjusting operation will not be able to be well made.
U.S. Pat. No. 4,982,725 discloses an endoscope apparatus whereby, in case the insertable part bends to contact the object to be inspected, it will be quickly detected and further the contact will be avoided to improve the safety of the endoscope inspection.